Medical communities have become concerned over the possibility of accidental communication of disease, such as Acquired Immune Deficiency Syndrome (AIDS), hepatitis, and other diseases communicable through bodily fluids, through accidental needle sticking and improperly sterilized multiple-use needle injector. One way to curb some of these mishaps is to discard the entire needle injector after a single use.
A number of single use needle injectors have been contemplated in this regard, as described in U. S. Pat. Nos. 5,226,882 to Bates; 5,423,756 to van der Merwe; 5,135,507 to Haber et al; and 5,407,431 to Botich et al. As with all needle injectors, they provide a barrel for holding medication and a plunger/piston assembly slidingly received within the barrel for ejecting medication out of the barrel The Bates and van der Merwe patents disclose a piston (the forefront part that pushes medication) that separates from a plunger (the rod-like portion that pushes the piston) after medication is ejected. The Haber and Botich patents achieves a similar result by locking the piston to the barrel after the injection stroke is completed to prevent reuse.
Needleless injectors have no needle. They thus completely remove any apprehension or the possibility of being pierced. At least in this regard, the needleless injectors are superior in eliminating accidental disease transmission. Different needleless injector types have been contemplated, as described, for instance, in U.S. Pat. Nos. 5,062,830 issued to Dunlap; 4,790,824 to Morrow et al.; 4,623,332 to Lindmayer et al.; 4,421,508 to Cohen; 4,089,334 to Schwebel et al.; 3,688,765 to Gasaway; 3,115,133 to Morando; 2,816,543 to Venditty et al.; and 2,754,818 to Scherer. These injectors have been contemplated to administer medication as a fine, high velocity jet, delivered under sufficient pressure to enable the jet to pass through the skin tissue without requiring a hypodermic needle. These injectors typically have a nozzle assembly which has a barrel-like nozzle body for holding medication therein. The nozzle member has an orifice through which a jet stream of medication is forced out from the chamber when a plunger/piston is actuated by an energy source, such as a coil spring, gas spring, and gas cartridge.
Even though needleless injectors eliminate known problems associated with the needle injector type, nevertheless, as an added safety precaution, it would be desirable to discard the nozzle assembly after each use to prevent its reuse. For example, after a single use the high pressure applied by the energy source may cause the seal between the plunger/piston and the nozzle assembly to partially fail or leak. Thereafter, a subsequent use of the same nozzle may have inadequate pressure transmitted to the medication to ensure proper delivery. Additionally, this high pressure may enlarge the orifice in the nozzle assembly so that subsequent uses of the same assembly would not produce a jet having sufficient velocity to penetrate to a desired depth.